Whitespace cleanup
Refactor `msuac` class to use `registry::value`

Without this commit, the `msuac` class was declaring directly a
different type for the registry key and the associated value. This is
unnecessary since there is the `registry::value` defined type that will
control the value and optionally control the key existence if it is not
yet declared.

This commit refactors the `msuac` class to use the `registry::value`
defined type in favor of separate declarations. It also uses different
names for the variables the get set to the value data in order to make
the usage more clear.
Merge pull request #1 from trlinkin/master

Refactor and clean up `msuac` class